1. Field of the Invention
The present invention relates to a method calculating the intensity of an electromagnetic field emitted from an electric circuit device, and more particularly, to a method and device generating data input to an electromagnetic field intensity calculating device which calculates the intensity of an electromagnetic field emitted from an electric circuit device by using a moment method.
2. Description of the Related Art
The electromagnetic field intensity of an electromagnetic wave emitted from an object having an arbitrary shape, for example, an electric circuit device can be easily calculated if an electric current which flows in each part of the object is known. Theoretically, the value of an electric current is given by solving the Maxwell""s electromagnetic field equations under a given boundary condition. However, there is no theoretical solution to an object having an arbitrary shape under a complex condition.
Accordingly, all of electric current calculation methods used in a current electromagnetic field intensity calculating device are approximation methods. Three methods such as an infinitesimal loop antenna approximation method, a distributed constant line approximation method, and a moment method are known as the approximation solutions.
The infinitesimal loop antenna approximation method is a method with which a wire interconnecting a wave source circuit and a load circuit is handled as a loop antenna, and an electric current on the loop is obtained with a calculation of a lumped constant circuit by assuming that the electric current on the loop is flat. Although the calculation of this method is the simplest, its accuracy is low under a condition that the size of a loop cannot be ignored in comparison with the wavelength of an electromagnetic wave.
The distributed constant line approximation method is a method with which an electric current is obtained by applying the distributed constant line equations to an object that can be approximated to a one-dimensional structure. Its calculation is relatively easy, and an electric current can be quickly obtained with high accuracy. However, for an object to be analyzed, which cannot be approximated to a one-dimensional structure, by way of example, an object having an arbitrary shape such as a printed circuit board, a metal cabinet, etc., an electric current cannot be obtained.
In the meantime, the moment method is one solution of integral equations derived from the Maxwell""s electromagnetic field equations, and can handle a three-dimensional object having an arbitrary shape. With this method, an object is partitioned into small elements (patches or meshes), and an electric current is calculated.
If the intensity of an electromagnetic field emitted from an electric circuit device is calculated with the moment method, it can be calculated with high accuracy by combining all of constituent elements such as a printed circuit board, a cable, a lead, a metal cabinet, etc. within the electric circuit device, and by accurately putting the device into a model.
Three-dimensional data and data of wires are captured from a CAD as data of a printed circuit board, a cable, a lead, etc., so that an analysis model can be generated with relative ease. However, for three-dimensional structure data such as the metal cabinet of an electric circuit device, etc., a mesh model must be generated by partitioning the data into meshes (patches) which are suitable for the moment method after capturing the data from a CAD. At this time, the model must be generated accurately and efficiently.
Conventionally, a metal cabinet of an electric circuit device, etc. is conventionally partitioned into meshes (patches) shaped like triangles each of which is configured by 3 points, as an automatic partitioning method, even if the metal cabinet, etc. is partitioned into meshes which are suitable for the moment method. As will be described later, a mesh partitioning method that is most suitable for the moment method is a method partitioning into quadrilaterals. Conventionally, however, it is difficult to automatically partition a metal cabinet, etc. into quadrilateral meshes each of which is configured by four points.
That is, conventionally, for a portion that cannot be partitioned as a quadrilateral, or a portion having a hole, CAD data must be manually changed so that a CAD model must be modified to a form suitable for partitioning into quadrilateral meshes. This requires much time and labor.
FIGS. 1, 2A, and 2B explain the influences that different mesh shapes exert on an electric current calculation using the moment method. FIG. 1 explains the difference between electric current calculations within meshes (patches). In this figure, electric currents flowing from vertexes to the directions (indicated by arrows) of opposite sides are calculated for a triangle mesh, whereas electric currents flowing to the directions of opposite sides are calculated for a quadrilateral mesh.
FIGS. 2A and 2B explain the directions of electric currents as a whole in the case where such meshes are combined. If partitioning is made into triangle meshes as shown in FIG. 2A, the flow of an electric current becomes zigzag, namely, uneven, and the length of a path on which the electric current flows becomes longer. As a result, a propagation delay of the electric current occurs, and the accuracy of an analysis made with the moment method is degraded. In the meantime, if partitioning is made into quadrilateral meshes, an electric current smoothly flows, and the accuracy of an analysis made with the moment method is improved.
An object of the present invention is to improve the analysis accuracy of an electromagnetic field intensity calculation as a whole, and to increase an efficiency of the process of the electromagnetic field intensity calculation in view of the above described problem by automatically partitioning a metal cabinet of an electric circuit device, etc. into quadrilateral meshes which are suitable for an electric current calculation using the moment method, and by providing the partitioned data to an electromagnetic field intensity calculating device.
A method generating data input to an electromagnetic field intensity calculating device according to the present invention, which is a method generating data input to an electromagnetic field intensity calculating device that calculates the intensity of an electromagnetic field emitted from an electric circuit device having a metal cabinet, extracts surface data of the metal cabinet from three-dimensional data of the electric circuit device, partitions the surface corresponding to the surface data into quadrilateral meshes, and outputs the data partitioned into meshes to the electromagnetic field intensity calculating device.
According to the present invention, a metal cabinet model which is suitable for a calculation of the moment method, namely, a model partitioned into quadrilateral meshes can be automatically and quickly generated from the three-dimensional structure data of a CAD system, and such a model is output to an electromagnetic field intensity calculating device, thereby accurately calculating the intensity of an electromagnetic field emitted from the whole of an electric circuit device including its metal cabinet. This can greatly contribute to an improvement in the practicality of the electromagnetic field intensity calculating device.